Ability of αs-casein to suppress the heat aggregation of ovotransferrin

The effects of alphas-casein on heat aggregation of ovotransferrin (OT) were studied by heating at 80 degreesC for 20 min in 10 mM phosphate buffer, pH 7.0. The heat interactions between alphas-casein and OT were followed by turbidity development and polyacrylamide gel electrophoresis. We found that alphas-casein can effectively suppress the heat-induced aggregation of heat-labile OT. The suppressive ability of as-casein was reduced by the presence of NaCl on heating. Dephosphorylated as-casein had less ability to suppress the aggregation of OT than native as-casein. Our results indicate that alphas-casein interacts with the heat-denatured OT through its exposed hydrophobic surface and phosphoserine residue. Such interactions seem to be important in helping to suppress the aggregation of heated OT. The suppressive effects of alphas-casein on heat aggregation of OT would be partially ascribed to the formation of transparent gel from egg white by the addition of as-casein.